Java Hashmap 实现来计算每个字符的出现次数
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Hashmap implementation to count the occurrences of each character
提问by Sumithra
The below code is to count the occurence of each character and it should print the count. But with the code I have tried I get only a 1 I don't know the changes I should make.
下面的代码是计算每个字符的出现次数，它应该打印计数。但是使用我尝试过的代码，我只得到 1 我不知道我应该做哪些改变。
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
class Count_CharMap {
public static void main(String[] args) {
try
{
FileInputStream file = new FileInputStream("D:\trial.txt");
DataInputStream dis = new DataInputStream(file);
BufferedReader br = new BufferedReader(new InputStreamReader(dis));
String Contents="";
String str="";
while ((Contents = br.readLine()) != null) {
str+=Contents;
}
char[]char_array =str.toCharArray();
int count = 0;
char ch = char_array[count];
Map<Character,Integer> charCounter=new HashMap<Character,Integer>();
for(int i=0;i<str.length();i++)
{
if(charCounter.containsKey(char_array[i]))
{
charCounter.put(ch, charCounter.get(ch)+1);
}
else
{
charCounter.put(ch, 1);
}
}
for(Character key:charCounter.keySet())
{
System.out.println(key+""+charCounter.get(key));
}
}
catch(IOException e1){
System.out.println(e1);
}
}
}
Actual output should be like If i have abcdabc in my trial.txt it should print a 2 b 2c 2 d 1.
实际输出应该像如果我的trial.txt中有abcdabc，它应该打印a 2 b 2c 2 d 1。
采纳答案by Paul
You're leaving char ch set as the same character through each execution of the loop.
在每次执行循环时，您都将 char ch 设置为相同的字符。
It should be:
它应该是：
ch = char_array[i];
if(charCounter.containsKey(ch)){
charCounter.put(ch, charCounter.get(ch)+1);
}
else
{
charCounter.put(ch, 1);
}
Inside the for loop.
在 for 循环内。
回答by atiruz
import java.util.HashMap;
import java.util.Map;
...
Map<String, Integer> freq = new HashMap<String, Integer>();
...
int count = freq.containsKey(word) ? freq.get(word) : 0;
freq.put(word, count + 1);
回答by user1581734
Hai All The below code is to count the occurrence of each character and it should print the count. may be helps you..Thanks for seeing
Hai All 下面的代码是计算每个字符的出现次数，它应该打印计数。可能对你有帮助..谢谢你看到
package com.corejava;
包 com.corejava;
import java.util.Map;
import java.util.TreeMap;
public class Test {
public static void main(String[] args) {
String str = "ramakoteswararao";
char[] char_array = str.toCharArray();
System.out.println("The Given String is : " + str);
Map<Character, Integer> charCounter = new TreeMap<Character, Integer>();
for (char i : char_array) {
charCounter.put(i,charCounter.get(i) == null ? 1 : charCounter.get(i) + 1);
}
for (Character key : charCounter.keySet()) {
System.out.println("occurrence of '" + key + "' is "+ charCounter.get(key));
}
}
}
回答by Vitalii Fedorenko
Java 8 streams:
Java 8 流：
Map<String, Long> map =
Arrays.stream(string.split("")).
collect(Collectors.groupingBy(c -> c, Collectors.counting()));
Guava HashMultiset:
番石榴哈希多集：
Multiset<Character> set = HashMultiset.create(Chars.asList("bbc".toCharArray()));
assertEquals(2, set.count('b'));
回答by shyam karwa
inside the for loop
在 for 循环内
ch = char_array[i];
charCounter.put(charCounter.contains(ch)?charCounter.get(ch)+1:1);
ch = char_array[i];
charCounter.put(charCounter.contains(ch)?charCounter.get(ch)+1:1);
回答by Teju J Gowda
import java.util.TreeMap;
public class OccuranceDemo {
public static void main(String[] args) {
TreeMap<String , Integer> mp=new TreeMap();
String s="rain rain go away";
String[] arr = s.split(" ");
int length=arr.length;
for(int i=0;i<length;i++)
{
String h = arr[i];
mp.put(h, mp.get(h)==null?1:mp.get(h)+1);
}
System.out.println(mp.get("go"));
}
}
回答by Nikhil M
String str=new String("aabbbcddddee");
char[] ch=str.toCharArray();
HashMap<Character,Integer> hm=new HashMap<Character,Integer>();
for(char ch1:ch)
{
if(hm.containsKey(ch1))
{
hm.put(ch1,hm.get(ch1)+1);
}
else
{
hm.put(ch1,1);
}
}
Set s1=hm.entrySet();
Iterator itr=s1.iterator();
while(itr.hasNext())
{
Map.Entry m1=(Map.Entry)itr.next();
System.out.println(m1);
}
回答by T.gautam
import java.util.*;
public class Test {
public static void main(String[] args) {
String str = "STACKOVERFLOW";
char[] char_array = str.toCharArray();
System.out.println("The Given String is : " + str);
Map<Character, Integer> charCounter = new TreeMap<Character, Integer>();
for (char i : char_array) {
charCounter.put(i,charCounter.get(i) == null ? 1 : charCounter.get(i) + 1);
}
for (Character key : charCounter.keySet()) {
System.out.println("occurrence of '" + key + "' is "+ charCounter.get(key));
}
}
}
回答by Kailas Kakade
public void mapPractices() {
公共无效地图实践（）{
Map<Character, Integer> map = new HashMap<>();
String dataString = "!@#$%^&*()__)(*&^%$#@!@#$%^&*(*&^%$#@!@#$%^&*()(*&^%$#@!@#$%^&*()(*&^%$#@!@#$%^&*()(*&^%$#";
for (int i = 0; i < dataString.length(); i++) {
char charAt = dataString.charAt(i);
if (map.containsKey(charAt)) {
int val = map.get(charAt);
map.put(charAt, val+1);
} else {
map.put(charAt, +1);
}
}
System.out.println("Characters ant the string=" + map);
}
